Question:medium

An engine running at 150 rpm drives a line shaft by means of a belt. The engine pulley is 750 mm diameter and the pulley on the line shaft being 450 mm. A 900 mm diameter pulley on the line shaft drives a 150 mm pulley keyed to a dynamo shaft. The speed of dynamo shaft in rpm will be

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For compound belt drives, you can find the final speed in a single step using the compound ratio:
\[ N_{\text{final}} = N_{\text{initial}} \times \left( \frac{d_1}{d_2} \times \frac{d_3}{d_4} \right) \] \[ N_{\text{final}} = 150 \times \left( \frac{750}{450} \times \frac{900}{150} \right) = 150 \times \left( \frac{5}{3} \times 6 \right) = 150 \times 10 = 1500 \text{ rpm} \]